GLP-1(7-36) protected against oxidative damage and neuronal apoptosis in the hippocampal CA region after traumatic brain injury by regulating ERK5/CREB.

BACKGROUND: Glucagon-like peptide-1 (GLP-1) (7-36) amide, an endogenous active form of GLP-1, has been shown to modulate oxidative stress and neuronal cell survival in various neurological diseases. OBJECTIVE: This study investigated the potential effects of GLP-1(7-36) on oxidative stress and apoptosis in neuronal cells following traumatic brain injury (TBI) and explored the underlying mechanisms. METHODS: Traumatic brain injury (TBI) models were established in male SD rats for in vivo experiments. The extent of cerebral oedema was assessed using wet-to-dry weight ratios following GLP-1(7-36) intervention. Neurological dysfunction and cognitive impairment were evaluated through behavioural experiments. Histopathological changes in the brain were observed using haematoxylin and eosin staining. Oxidative stress levels in hippocampal tissues were measured. TUNEL staining and Western blotting were employed to examine cell apoptosis. In vitro experiments evaluated the extent of oxidative stress and neural apoptosis following ERK5 phosphorylation activation. Immunofluorescence colocalization of p-ERK5 and NeuN was analysed using immunofluorescence cytochemistry. RESULTS: Rats with TBI exhibited neurological deterioration, increased oxidative stress, and enhanced apoptosis, which were ameliorated by GLP-1(7-36) treatment. Notably, GLP-1(7-36) induced ERK5 phosphorylation in TBI rats. However, upon ERK5 inhibition, oxidative stress and neuronal apoptosis levels were elevated, even in the presence of GLP-1(7-36). CONCLUSION: In summary, this study suggested that GLP-1(7-36) suppressed oxidative damage and neuronal apoptosis after TBI by activating ERK5/CREB.

PB1 domain-dependent signaling complex is required for extracellular signal-regulated kinase 5 activation.

MEKK2, MEK5, and extracellular signal-regulated kinase 5 (ERK5) are members of a three-kinase cascade for the activation of ERK5. MEK5 is the only MAP2K to express a PB1 domain, and we have shown that it heterodimerizes with the PB1 domain of MEKK2. Here we demonstrate the MEK5 PB1 domain is a scaffold that also binds ERK5, functionally forming a MEKK2-MEK5-ERK5 complex. Reconstitution assays and CFP/YFP imaging (fluorescence resonance energy transfer [FRET]) measuring YFP-MEKK2/CFP-MEK5 and CFP-MEK5/YFP-ERK5 interactions define distinct MEK5 PB1 domain binding sites for MEKK2 and ERK5, with a C-terminal extension of the PB1 domain contributing to ERK5 binding. Stimulus-dependent CFP/YFP FRET in combination with mutational analysis was used to define MEK5 PB1 domain residues critical for the interaction of MEKK2/MEK5 and MEK5/ERK5 required for activation of the ERK5 pathway in living cells. Fusion of the MEK5 PB1 domain to the N terminus of MEK1 confers ERK5 regulation by a MAP2K normally regulating only ERK1/2. The MEK5 PB1 domain confers stringent MAP3K regulation of ERK5 relative to more promiscuous MAP3K control of ERK1/2, JNK, and p38.

Genistein induces cell apoptosis in MDA-MB-231 breast cancer cells via the mitogen-activated protein kinase pathway.

Genistein, an isoflavonoid present in soybeans, exhibits anti-carcinogenic effects. Several studies have shown that genistein inhibits cell proliferation and triggers apoptosis in human breast cancer cells. In this study, we assessed the role of the MEK-ERK cascade in the regulation of genistein-mediated cell apoptosis in MDA-MB-231 cells. The results indicate that genistein, in a concentration-dependent manner, suppresses the protein levels of MEK5, total ERK5, and phospho-ERK5, effects that are consistent with inhibition of cell growth and induction of apoptosis. Exposure of these cells to genistein results in a concentration-dependent decrease in NF-kappaB/p65 protein levels and DNA-binding activity of NF-kappaB. Genistein down-regulates Bcl-2 and up-regulates Bax. NF-kappaB binding sites are present in the promoter of Bcl-2, suggesting that genistein might inhibit the expression of Bcl-2 through down-regulation of NF-kappaB. Exposure of MDA-MB-231 cells to genistein results in cleavage of caspase-3 and induction of caspase-3 activity in a concentration-dependent manner. Genistein inhibits NF-kappaB activity via the MEK5/ERK5 pathway; it also inhibits cell growth and induces apoptosis. In conclusion, inhibition of the MEK5/ERK5/NF-kappaB pathway may be an important mechanism by which genistein suppresses cell growth and induces apoptosis.

A licorice extract reduces lipopolysaccharide-induced proinflammatory cytokine secretion by macrophages and whole blood.

BACKGROUND: Periodontal diseases are a group of inflammatory disorders initiated by specific Gram-negative periodontopathogenic bacteria that lead to the destruction of tooth-supporting tissues. In this study, we tested whether a carbon dioxide-supercritical extract of Glycyrrhiza uralensis (licorice) can reduce the periodontopathogen-induced inflammatory response. METHODS: Monocyte-derived macrophages were treated with various concentrations of the licorice extract prior to being stimulated with Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) and Porphyromonas gingivalis lipopolysaccharide (LPS). The capacity of the licorice extract to mediate the inflammatory response was also tested in an ex vivo whole blood model stimulated with P. gingivalis LPS. The secretion of interleukin (IL)-1beta, -6, and -8 and tumor necrosis factor-alpha (TNF-alpha) in both models was assessed by enzyme-linked immunosorbent assays. Changes in the phosphorylation state of macrophage intracellular kinases induced by A. actinomycetemcomitans LPS and the licorice extract in the macrophage model were characterized by immunoblotting. RESULTS: The licorice extract exhibited potent anti-inflammatory properties, inhibiting the periodontopathogen LPS-induced IL-1beta, -6, and -8 and TNF-alpha responses of macrophages. The licorice extract inhibited the phosphorylation of important macrophage intracellular signaling proteins, including nuclear factor-kappa B p65 nuclear transcription factor and Jun proto-oncogene-encoded activator protein (AP) 1 transcription factor, which are involved in inflammatory signaling pathways. The licorice extract was also a potent inhibitor of the proinflammatory cytokine response in the ex vivo human whole blood model. CONCLUSION: This CO(2)-supercritical licorice extract is a potential candidate for the development of a new therapy to prevent and/or treat periodontitis-associated tissue destruction.

Scutellarin attenuates vasospasm through the Erk5-KLF2-eNOS pathway after subarachnoid hemorrhage in rats.

Angiographic vasospasm, especially in the early phases (<72h) of subarachnoid hemorrhage (SAH), is one of the major complications after an aneurysm rupture and is often the cause of delayed neurological deterioration. Scutellarin (SCU), a flavonoid extracted from the traditional Chinese herb Erigeron breviscapus, has been widely accepted as an antioxidant, but the effect of SCU on vasospasm after SAH remains elusive. Endovascular perforation was conducted to induce SAH in Sprague-Dawley rats. Then, the underlying mechanism of the anti-vasospasm effect of SCU was investigated using a modified Garcia scale, India ink angiography, cross-sectional area analysis, immunohistochemistry staining and western blot. SCU (50µM, 100mg/kg) alleviated angiographic vasospasm and improved neurological function 48h after SAH and enhanced the expression of endothelial nitric oxide synthase (eNOS) at the intima of cerebral arteries. In addition, SCU upregulated the expression of phosphorylated extracellular-regulated kinase 5 (p-Erk5) and Kruppel-like factor 2 (KLF2) at 48h after SAH. However, the effects of SCU were reversed by the Erk5 inhibitor XMD8-92. Our results indicate that SCU could attenuate vasospasm and neurological deficits via modulating the Erk5-KLF2-eNOS pathway after SAH, which may provide an experimental basis for the clinical use of SCU treatment in SAH patients.